1. Field of the Invention
The invention relates to an LED package and, particularly, to an LED package to radiate light emitted from a light emitting diode (hereinafter referred to as LED) through an optical system in a predetermined direction and range.
2. Description of the Related Art
Conventionally, a lens-type LED package is well known that uses a light emitting element as light source and is designed to radiate light emitted from the light emitting element in a predetermined direction while controlling its lighting distribution by using an optical system (e.g., Japanese patent application laid-open No.8-107235 (prior art 1)).
However, in the lens-type LED package, it is impossible to secure a sufficient solid angle of lens surface to the light emitting element when it is provided with an optical surface shape to enhance the convergence performance. Therefore, it can only control about 30% of light emitted from the light emitting element and, thus, cannot offer a high efficiency of external radiation. So, prior art 1 discloses an LED package that is provided with a reflection surface around the light emitting element.
FIG. 1 is a cross sectional view showing the LED package disclosed in prior art 1.
The LED package is composed of an LED 60 as light source and a lens 61 to radiate converging light L emitted from the LED 60.
The lens 61 has a cylindrical recess 61A formed at the center of a nearly truncated cone, a semispherical convex lens 61B provided in the recess 61A, a space 61D with a circular cross section formed at a minor bottom face 61C, and a reflection surface 61E to form its side face. The LED 60 is disposed at the center of space 61D.
In this LED package, light emitted from the LED 60 is radiated parallel to the center axis of lens 61 while being is converged by the convex lens 61B. Also, light emitted in the direction of reflection surface 61E from the LED 60 is totally reflected on the reflection surface 61E and is then radiated parallel to the center axis of lens 61. Thus, since light emitted from the LED 60 is radiated parallel to the center axis of lens 61 based on total reflection and convergence, the lighting intensity at a point of equal distance can be increased.
However, the conventional LED package needs to use a large reflection mirror so as to efficiently control light not to be entered to the lens. Namely, as shown in FIG. 1, the reflection surface 61E needs to be further extended to a high level so as to efficiently control light not to be entered to the lens. A solid angle A of reflection surface 61A to the light emitting element 51 corresponding to that extension is big and the radiation intensity of light emitting element 51 is also intensive in this direction. Therefore, the amount of light to be controlled by the extension becomes considerable.
On the other hand, when using such a large reflection mirror, the diameter DL of lens to the outer diameter DW becomes relatively small. If the outer diameter DW is set small, then the homothetic ratio of lens diameter to emission area of light source has to be improper and, therefore, a problem is generated that, due to the lowering of convergence performance, it becomes impossible to radiate light with sufficient brightness in a desired direction and range. In addition, when the light source (LED) is enlarged according to the demand for high brightness or high output and its emission area is thereby enlarged, the homothetic ratio becomes improper. Thus, the same problem is generated.
Meanwhile, another LED package is suggested that uses a total reflection at its radiation surface to radiate light reflected on its reflection surface so as to offer a lower profile as well as enhancing the external radiation efficiency. However, in such an LED package, incident light to the reflection surface needs to have two optical paths and, therefore, a high convergence performance cannot be obtained.